Common Questions About Pacemakers

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Pacemakers are indicated in patients with certain symptomatic bradyarrhythmias caused by sinus node dysfunction, and in those with frequent, prolonged sinus pauses. Patients with third-degree or complete atrioventricular (AV) block benefit from pacemaker placement, as do those with type II second-degree AV block because of the risk of progression to complete AV block. The use of pacemakers in patients with type I second-degree AV block is controversial. Patients with first-degree AV block generally should not receive a pacemaker except when the PR interval is significantly prolonged and the patient is symptomatic. Although some guidelines recommend pacemaker implantation for patients with hypersensitive carotid sinus syndrome, recent evidence has not shown benefit. Some older patients with severe neurocardiogenic syncope may benefit from pacemakers, but most patients with this disorder do not. Cardiac resynchronization therapy improves mortality rates and some other disease-specific measures in patients who have a QRS duration of 150 milliseconds or greater and New York Heart Association class III or IV heart failure. Patients with class II heart failure and a QRS of 150 milliseconds or greater also appear to benefit, but there is insufficient evidence to support the use of cardiac resynchronization therapy in patients with class I heart failure. Cardiac resynchronization therapy in patients with a QRS of 120 to 150 milliseconds does not reduce rates of hospitalization or death.

Deciding when a pacemaker should be placed can be a complicated decision. This article reviews some of the various indications for pacemaker placement.


Clinical recommendationEvidence ratingReferencesComment

Sinus node dysfunction and AV block

Pacemakers should be placed for patients with sinus node dysfunction resulting in symptomatic bradyarrhythmias, frequent sinus pauses of at least three seconds, or chronotropic incompetence.


1, 37

Recommendation from consensus guidelines based on expert opinion

Pacemaker placement may be considered for patients who have a heart rate less than 40 beats per minute and intermittent symptoms consistent with bradycardia, but in whom bradycardia has not been documented at the time the symptoms occur.


1, 7

Pacemaker placement may be considered for patients with syncope of unexplained origin in whom clinically significant abnormalities of the sinus node are found or induced during an electrophysiologic study.


1, 7

Pacemaker placement may be considered for patients who have a daytime heart rate less than 40 beats per minute and minimal symptoms.


1, 7

There is a strong indication for pacemaker placement in patients with third-degree or type II second-degree AV block.


1, 712

Recommendation based on consensus guidelines

The decision to place a pacemaker for patients with type I second-degree AV block is controversial; the American College of Cardiology/American Heart Association recommends placement for symptomatic patients and for asymptomatic patients with an infra- or intra-Hisian block found at the time of the electrophysiologic study.


1, 3, 7, 13

Recommendations based on expert opinion and small cohort studies

Pacemaker placement is not indicated for patients with asymptomatic first-degree AV block.


1, 7, 14

Pacemaker placement should be considered for patients with symptomatic first-degree AV block and a PR interval greater than 0.3 seconds.


1, 7, 14, 15

Hypersensitive carotid sinus syndrome and neurocardiogenic syncope

There is insufficient evidence to support the use of pacemakers in patients with hypersensitive carotid sinus syndrome, despite recommendations based on expert opinion.


16, 17

Recommendation based on a Cochrane systematic review and randomized, double-blind, controlled trial

There is insufficient evidence to support the use of pacemakers in patients with neurocardiogenic syncope, except in a limited population with severe symptoms.


16, 18

Recommendation based on a Cochrane systematic review and randomized controlled trial

Heart failure

Cardiac resynchronization therapy is indicated in patients with NYHA class II to IV heart failure and a QRS duration greater than 150 milliseconds.


1, 7, 1922

Consistent across meta-analyses and guidelines

There is insufficient evidence to support the use of cardiac resynchronization therapy in patients with NYHA class I heart failure and in those with a QRS of 120 to 150 milliseconds.


7, 20, 22

Conclusions from meta-analysis and guidelines differ regarding QRS interval indications

AV = atrioventricular; NYHA = New York Heart Association.

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to


The Authors

KERI L. DENAY, MD, is a clinical lecturer in the Departments of Family Medicine and Orthopaedic Surgery at the University of Michigan Medical School in Ann Arbor.

MICHAEL JOHANSEN, MD, is an assistant professor of family medicine at The Ohio State University College of Medicine in Columbus.

Address correspondence to Keri L. Denay, MD, University of Michigan Medical School, Briarwood Family Medicine, 1801 Briarwood Cir., Ann Arbor, MI 48109-5734. Reprints are not available from the authors.


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